1. Field of the Invention
The present invention relates to optical communications systems and, more specifically, to optically transparent networks.
2. Description of the Related Art
An optically transparent network has a plurality of nodes connected by optical links and operated so that optical communication signals are transmitted from a source node, through one or more transit nodes (if any), to a destination node without being converted into electrical signals at any point along the way. A mesh network is a network in which, with the exception of nodes in certain terminal branches, two or more different communication paths exist for connecting any pair of nodes. Mesh networking is advantageous because, generally, it enables continuous connections and reconfiguration around blocked communication paths by hopping from node to node until a connection can be established.
One approach to coordinating control operations performed at different nodes of an optically transparent mesh network is to subdivide the network into relatively topologically simple control domains, e.g., rings, lines, etc. However, this approach limits the available network topologies. In addition, for a network having a relatively complex topology, it might be difficult to determine what constitutes a ring or a line. This difficulty might cause the subdivisions to become more and more arbitrary as the network complexity increases.
Other known methods for coordinating control operations in an optically transparent mesh network rely on provisioning global information about the network at each node of the network. However, this approach complicates the network deployment because control domains have to be defined before the deployment and information about the control domains has to be provisioned at the nodes. Any modifications to the network effected during the actual deployment then have to be reflected in the provisioned information. Disadvantageously, tracking and maintaining the integrity of that information can significantly increase the operational costs for the network.
An additional problem with using predefined control domains is that, in many cases, the optimal configuration of control domains might change when the network is expanded or otherwise reconfigured. The network's hardware might be modified, e.g., when new optical amplifiers are deployed, or a “soft” change might be implemented, e.g., when a new communication channel (wavelength) is added to the system. Because most control operations are sensitive to both the network's hardware and traffic distribution, both “hard” and “soft” changes need to be accounted for in the provisioned information, which further increases the operational costs.